COMPOSITE GASKET

Abstract: A combined gasket which can improve various characteristics which differ in accordance with the conditions under which it is used by maintaining sealability by combining a sealing material (6) selected in accordance with the properties of sheet-like sealing materials (1A, 1B) of a gasket base (4). This combined gasket is constructed such that a plurality of slits (5) are formed thicknesswise in the surface (1a) of sheet-like sealing materials (1A, 1B) composing a gasket base (4) and that a sealing material (6) composed of a material different from the material composing the sealing materials (1A, 1B) is filled in the slits (5) and applied to the surface (1a) of the sealing materials (1A, 1B).

Description: Technical Field The present invention relates to a composite gasket which is useful for sealing a flange connection portion of a pipe joint, a passage connection portion of a fluid apparatus, or the like, and more particularly to a sheet-like composite gasket which is cut out in an arbitrary shape from a large sheet base material, and then used. Background Art Conventionally, such gaskets practically used include many types such as a gasket configured by a single body of a sheet-like seal material composed of expanded graphite, or the like, and a gasket in which a sheet-like seal material and a reinforcing material such as metal foil are stacked to be formed into one piece in order to ensure strength. For example, Fig. 15 shows a gasket 100 which is composed by interposing and fixing a sheet-like reinforcing material 103 in a sandwich-like manner between two sheet-like seal materials 101A, 101B in a thickness direction through adhesive agents 102A, 102B. Fig. 16 shows a gasket 100 which is composed by interposing and fixing a reinforcing plate 104 wherein raised pieces 104a are partially formed, between the sheet-like seal materials 101A, 101B in the thickness direction. In the above-mentioned prior art gaskets, the properties of the sheet-like seal materials 101A, 101B directly affect the properties required as a gasket. In a gasket using the sheet-like seal materials 101A, 101B composed of an expanded graphite sheet, for example, there arises no problem in leakage along contact surfaces which is due to reduced surface draping properties for a flange face, etc. as shown in Figs. 17 and 18, but the existence of gaps 105 in internal layers causes penetration leakage of a sealing fluid Q to easily occur. In place of an expanded graphite sheet, a porous polytetrafluoroethylene (PTFE) sheet, a joint sheet, or a beater sheet may be used as the sheet-like seal materials 101A, 101B. Also in all cases where such materials are used, however, there arise problems due to the defects shown in Fig. 18. In the case of a calcined sheet made of PTFE, there is a problem in leakage along contact surfaces and creep due to red-Liced surface draping properties. A combined gasket is already disclosed in JP-A-56076257 which describes two kinds of seal materials of a resilient rubber material consisting of a frame with tongues and plastic seal fillers disposed between the tongues. The disclosed packing is utilized for a segment joint used for shield technique and the packing is sealed by the surface contact and engagement between the tongues. In case the surface contact is incomplete it is occluded by the plastic filler. There is no provision for the sealing of the many fine pores inside of the conventional seal materials which communicate with the outside thereof. The same is true for the gasket as disclosed in JP-A-57057773 which consists of a string-like fixed form sealing material in combination with a water sealing material. The citation does not refer to any provisions for penetration prevention of sheet-like seal material having fine pores. Also the JP-Y-2-40350 relates to a technique of increasing the contact surface pressure of sheet gaskets by providing a reinforcernent material on the sheet-like expanded graphite with projections being formed on the surface of the reinforcement material disposed inside of the seal material. The description does not disclose any provision for penetration leakage prevention with respect to sheet-like seal material having fine pores. The present invention has been conducted in view of the above-mentioned circumstances. It is an object of the invention to provide a composite gasket in which a sheet-like seal material is combined with a specific seal material in accordance with the use and the installation location, whereby leakage along contact surfaces, and penetration leakage from internal layers can be eliminated to improve the sealing properties. It is another object of the invention to provide a composite gasket which can improve various required properties which differ according to the use and the installation location. Disclosure of the Invention In order to attain the objects, the composite gasket of the invention is a composite 'gasket according to the features of claim 1. The loading includes the filling and the stacking. Only either of the filling and the stacking may be conducted. Alternatively, both the filling and the stacking may be conducted in parallel. As the sheet-like gasket substrate of the composite gasket having the above-mentioned configuration, a sheet-like seal material may be used singly, or a stack in which a sheet-like seal material is disposed on both the faces or one face (i.e., at least one of the faces) of a reinforcing material may be used. The reinforcing material includes stainless steel (SUS); metal foil or a thin plate of copper, aluminum, titanium, iron (SPCC); such foil or plate in which many holes are formed; a plastic film; a net (mesh). The slits of the composite gasket having the above-mentioned configuration have a depth which is within a range of 10 to 100 % of the thickness of the sheet-like seal material in the gasket substrate, and preferably are continuously formed in such a manner that the surface of the gasket substrate is divided in a predetermined shape. As the sheet-like seal material in the gasket substrate, useful is a sheet selected from an expanded graphite sheet or a porous PTFE sheet. In the invention, unless otherwise specified, a porous PTFE sheet means a porous PTFE sheet which is not calcined and has a density of 0.2 to 1.8 g/cm 3 . As the joint sheet, useful are inorganic fiber or organic fiber such as glass fiber, aramid fiber, carbon fiber, or rock wool; and a combination of a binder such as synthetic rubber (for example, nitrile butadiene rubber: NBR), chloroprene rubber (CR), natural rubber (NR), silicone rubber, acrylic rubber, or PTFE, and a filler which is inorganic powder such as talc, sepiolite, chlorite, wollastonit, kaolin, clay, mica, or potassium titanate. As the seal material to be combined, useful is a substance selected from substances which are different from the substance constituting the sheet-like seal material in the gasket substrate, among substances including: impermeable substances which have no internal voids, such as rubber, resin, and grease; soft seal materials such as soft rubber, and soft resin; nonadhesive substances such as graphite, and mica; substanceswhich are excellent in corrosion prevention, such as a sacrificial metal, and adsorption anticorrosives; creep resistant substances which are obtained by filling organic fiber, inorganic fiber, in rubber or resin. The seal material to be combined is adequately selected from those described in detail below, in accordance with required properties which are to be improved depending on the use and the installation location of a gasket. (1-1) In the case where penetration leakage from internal layers and leakage along contact surfaces are required to be prevented from occurring: Impermeable materials which have no internal voids, specifically, rubber such as NBR, CR, silicon acrylic, and NR; resin such as epoxy, phenol, nylon, polyethylene, PTFE, and acrylic ester; high viscous oil such as silicone oil, and fluorooil; and grease such as paraffin wax, bees wax, and Japan wax. (1-2) In the case where improved surface draping properties are required: The same materials as those in (1-1) above, for example, soft epoxy resin, and a soft seal material such as soft rubber having a small rubber hardness. (1-3) In the case where a gasket is required not to bond to a flange: Nonadhesive substances such as graphite (scale-like graphite, earthy graphite and the like excluding expanded graphite), layer minerals such as mica, PTFE resins including porous PTFE, silicon, and polyethylene; wax; silicone oil; and fluorooil. (1-4) In the case where flanges are required not to be corroded: Grease such as petrolatum, and wax; adsorption anticorrosives such as mineral oil of the amine type or the like; and passivating agents such as nitrite. In the case where flanges are required not to be electrolyticcorroded: fine powder of a sacrificial metal such as zinc, and aluminum. (1-5) In the case where the surface friction force is required to be increased, scratch prevention (protection) of a surface is required, and creep protection is required: Materials in which inorganic short fiber such as carbonfiber, glass fiber, ceramic fiber, and rock wool, or organic fiber chops such as aramid fiber, phenol fiber; and inorganic powder such as talc, sepiolite, chlorite, wollastonite, kaolin, clay, mica, potassium titanate, and particularly fiber-, needle-, or flake-like one of these materials are combined as a filler with the rubber and resin materials listed in (1-1) and (1-2) above. According to the invention, a plurality of slits are formed in a surface of a sheet-like seal material in a gasket substrate, the slits elongating from the surface in the thickness direction, and a seal material composed of a substance which is different from the sheet-like seal material is loaded and/or stacked into the slits and/or the surface of the sheet-like seal material. Therefore, a large sheet base material may be produced, the sheet base material may be cut along slit lines in an arbitrary shape or size, and the cut out material may be used. When the seal material to be combined is adequately selected and used in accordance with the sheet-like seal material from substances which are different from the materials constituting the sheet-like seal material, moreover, the sheet-like seal material composed of the seal material which lacks in, for example, stretchability is provided with stretchability so that lamination separation is prevented from occurring in the case where a bending force is applied, and operability is improved. Furthermore, various problems in practical use of a gasket material including the sheet-like seal material can be solved, and various required properties which differ according to the use and the installation location of a gasket can be improved. The sheet-like seal material in the gasket substrate is configured by an expanded graphite sheet or a porous PTFE sheet which has excellent surface draping properties and is free from leakage along contact surfaces. Furthermore, an impermeable material such as described above is selected and used as the seal material to be combined. This can prevent penetration leakage from internal layers which constitutes a problem of such a sheet-like seal material, from occurring, and cooperate with surface draping properties, of the expanded graphite sheet or the porous PTFE sheet so as to extremely improve the sealing properties. As described above, when a seal material suitable for solving various problems which may be produced in materials constituting the sheet-like seal material in the gasket substrate is selected and used in accordance with the constituting materials, it is possible to obtain a composite gasket which can satisfy substantially all of properties required in a gasket of this kind, irrespective of the materials constituting the sheet-like seal material. In this case, since the amount of the seal material to be combined may be very small, the reduction of the properties which the materials constituting the sheet-like seal material intrinsically have is very small in degree. The depth of the slits formed in the sheet-like seal material in the gasket substrate is selected so as to be within the range of 10 to 100 % of the thickness of the seal material. The seal material to be combined can firmly be integrated with the gasket substrate by the anchor effect, and the effects of improving various properties can easily be attained in a satisfactory manner. If the depth of the slits was less than 10 % of the thickness of the seal material, the seal material to be combined could not sufficiently be integrated with the gasket substrate, and the seal material to be combined could be peeled off so that the predetermined effects of improving propertiescould not be attained. Brief Description of the Drawings Fig. 1 is a partial cutaway perspective view showing a- composite gasket according to a first embodiment of the invention. Fig. 2 is a cutaway perspective view in the case where slits are formed in the composite gasket of the first embodiment. Fig. 3 is a cutaway perspective view showing in an enlarged manner a part of the composite gasket of the first embodiment. Fig. 4 is an enlarged section view illustrating the function of the main portion of the composite gasket of the first embodiment. Fig. 5 is a partial cutaway perspective view showing a composite gasket according to a second embodiment of the invention. Fig. 6 is a cutaway perspective view showing in an enlarged manner a part of the composite gasket of the second embodiment. Fig. 7 is a partial cutaway perspective view showing a composite gasket according to a third embodiment of the invention. Fig. 8 is a partial cutaway perspective view showing a composite gasket according to a fourth embodiment of the invention which is in a state before pressurization. Fig. 9 is a partial cutaway perspective view showing the composite gasket according to the fourth embodiment which is in a state before pressurization. Fig. 10 is a table showing constituting conditions of main portions of the composite gaskets of the first to fourth embodiments. Fig. 11 is a plan view showing another shape of the slits. Fig. 12 is a plan view showing a further shape of the slits. Fig. 13 is a plan view showing a still further shape of the slits. Fig. 14 is a plan view showing a still further shape of the slits. Fig. 15 is a partial cutaway perspective view showing a prior art gasket. Fig. 16 is a partial cutaway perspective view showing another prior art gasket. Fig. 17 is an enlarged section view of the main portion of a prior art gasket and showing a state of occurrence of penetration leakage in a prior art gasket. Fig. 18 is a table showing problems of seal materials in prior art gaskets. Best Modes for Carrying Out the Invention Hereinafter, embodiments of the invention will be described with reference to the drawings. Fig. 1 is a partial cutaway perspective view showing a composite gasket according to a first embodiment of the invention. In Fig. 1, 1A and 1B designate a pair of sheet-like seal materials which are stacked in the thickness direction. Each of the sheet-like seal materials 1A, 1B consists of an expanded graphite sheet (see Fig. 10) A reinforcing material 2 is interposed in a sandwich-like manner between the seal materials 1A, 1B. The reinforcing material 2 is composed of, for example, SUS 304 or SUS 316L having a thickness of about 0.05 mm, and bonded to the seal materials 1A, 1B by respective thermoplastic or thermosetting adhesive agents 3A, 3B. The seal materials 1A, 1B, the reinforcing material 2, etc. constitute a sheet-like gasket substrate 4. As shown in Fig. 2, a plurality of splits 5 are formed in the surfaces 1a, 1b of the seal materials 1A, 1B. with starting from the respective surfaces 1a, 1b and elongating in the thickness direction. The depth of the slits is set to be within the range of 10 to 100 % of the thickness of the seal materials 1A, 1B. When the slits are to be deeply formed, for example, the depth is set to an extent that the slits may reach the adhesive agent layers 3A, 3B, respectively. The slits 5 are continuously formed in such a manner that the surfaces 1a, 1b of the pair of the seal materials 1A, 1B are divided in a predetermined shape, for example, a lattice-like shape. A seal material 6 which is composed of an impermeable material such as silicone rubber that is a substance different from the seal materials 1A, 1B is filled into the slits 5 as shown in Fig. 3. After the slits 5 are formed in the seal materials 1A, 1B made of an expanded graphite sheet, the seal material 6 composed of the silicone rubber is filled into the slits 5, and then local filling portions 6a of the seal material 6 are formed in the inner walls of the slits 5 as shown in Fig. 3, thereby exhibiting the anchor effect. This causes the seal material 6 to be firmly integrated with the seal materials 1A, 1B. According to the thus configured composite gasket, the filling of the seal material 6 composed of silicone rubber into the slits 5 provides stretchability to the seal materials 1A, 1B made of an expanded graphite sheet which is intrinsically inferior in stretchability, so that lamination separation which may occur in the cases such as that where a bending force is applied is suppressed. Furthermore, the gasket becomes easy to handle. Particularly, even when lamination gaps 7 such as shown in Fig. 4 are formed in the seal materials 1A, 1B, the silicone rubber 6 in the slits 5 functions as a seal material for penetration prevention to block the gaps 7. Consequently, penetration leakage of a sealing fluid Q is prevented from occurring. This cooperates with the intrinsic small leakage along contact surfaces which is originated in the use of the expanded graphite sheet, to extremely improve sealing properties of the whole of the gasket. A material which can improve other properties may suitably be mixed into the seal material 6 composed of silicone rubber. Fig. 5 is a partial cutaway perspective view showing a sheet-like composite gasket which was obtained as a second embodiment of the invention. In the embodiment, fluoro rubber is used as a seal material 16 which is filled into the slits 5, and also the surfaces of the seal materials 1A, 1B are covered in a ply manner by seal materials 17A, 17B composed of similar fluoro rubber, respectively. The other main portion is configured as shown in Fig. 10. Also in the composite gasket shown in the second embodiment, in the same manner as the first embodiment, the seal material 16 in the slits 5 is firmly integrated with the seal materials 1A, 1B by the anchor effect exerted by local filling portions 16a of the seal material, and penetration leakage from internal layers can be suppressed. Moreover, the whole area of the surfaces is covered by the seal materials 17A, 17B. When the gasket is used as a seal material for a flange connection portion of a pipe joint, therefore, there is a less fear that the gasket bonds to the flange surfaces, and sulfur or the like is prevented from directly contacting the flange surfaces so the corrosion of the flange surfaces can effectively be prevented from occurring. Fig. 7 is a partial cutaway perspective view showing a sheet-like composite gasket which was obtained as third embodiment of the invention. In the third embodiment, a porous PTFE sheet is used as a seal material 31, and the seal material 31 singly constitutes the gasket substrate 4. The slits 5 which pass through the seal material 31 in the thickness direction are formed in a lattice-like shape in the surface 31a of the seal material 31. A seal material 16 composed of fluoro rubber is filled into the slits 5. The other main portion is configured as shown in Fig. 10. Also in the composite gasket shown in the third embodiment, the seal material 31 composed of the porous PTFE sheet prevents the gasket from bonding to a flange surface, and the flange surface from being corroded, and the seal material 16 effectively prevents penetration leakage from internal layers from occurring. Figs. 8 and 9 are partial cutaway perspective views showing a sheet-like gasket which was obtained as a fourth embodiment of the invention. In the fourth embodiment, the gasket substrate 4 is configured in the same manner as that of the first embodiment. After the seal material 6 composed of silicone rubber is f illed into the slits 5 as shown in Fig. 8, the gasket substrate 4 having a thickness T is pressurized in the thickness direction so that the thickness is reduced to t as shown in Fig. 9. In the thus configured composite gasket of the fourth embodiment, the same effects as those of the embodiments described above can be attained, and the compression of the gasket substrate 4 in the thickness direction causes also the seal material 6 to be deformed in three-dimensional directions, thereby enhancing the strength. The depth of the slits 5 is not restricted to the values of the embodiments. As indicated by chain lines in Fig. 2, a value advantageous to properties to be improved is adequately selected and set within the range of 10 to 100 % of the thickness of the seal material 1A, (1B) (21) (31). In the embodiments described above, the slits 5 in the surface of the gasket substrate 4 have a lattice-like shape. This should be considered as an example. An arbitrary shape such as shown in Figs. 11 to 14 may be selected. Industrial Applicability As described above, according to the invention, slits are formed in the surface of a sheet-like seal material in a gasket substrate, the slits elongating from the surface in the thickness direction, and a seal material composed of a substance which is different from the seal material is loaded and/or stacked into the slits and/or the surface of the seal material. Therefore, a large sheet base material may be produced, the sheet base material may be cut in an arbitrary shape or size, and the cut out material may be used. When the seal material to be combined is adequately selected and used in accordance with the sheet-like seal material from substances which are different from the materials constituting the sheet-like seal material, moreover, even in the case where a substance having arbitrary properties is selected and used as the material constituting the sheet-like seal material in the gasket substrate, the invention can attain the effects that, while the reduction in properties is suppressed to a minimum level, various problems in practical use of the gasket substrate are solved, the sealing properties are ensured, and at the same time various required properties which differ according to the use and the installation location of a gasket are improved.

Claims: A composite gasket comprising a gasket substrate including a porous sheet-like seal material (1A, 1B; 101A, 101B) having communicating lamination gaps (7) inside the seal material characterized in that a plurality of slits (5) are formed in said sheet-like seal material, said slits (5) elongating from a surface of said sheet-like seal material (1A, 1B; 101A, 101B) from at least 10% to 100% of a thickness in the thickness direction. that said sheet-like seal material in said gasket substrate is selected from an expanded graphite sheet or a porous polytetrafluorethylene sheet and that a seal material (6) composed of a impermeable substance which is different from said sheet-like material having no internal voids is loaded and/or stacked into the slits and/or onto said surface of said sheet-like seal material. A composite gasket according to claim 1, wherein said gasket substrate is a single body of sheet-like seal material. A composite gasket according to claim 1 or 2, wherein said gasket substrate is configured by stacking a sheet-like seal material on at least one of the faces of a reinforcing material (3). A gasket according to anyone of claims 1 to 3, wherein said slits are continuously formed in such a manner that a surface of said gasket substrate is divided in a predetermined shape. A composite gasket according to claim 2, 3 or 4, wherein said seal material being combined is selected from substances which are different from the substance constituting the sheet-like seal material in said gasket substrate, said substances including: rubber, resin and grease; soft seal materials such as soft rubber and soft resin; non-adhesive substances such as graphite and mica; corrosion preventive substances, such as sacrificial metal and an adsorption anticorrosive; and creep resistant substances which are obtained by filling organic fiber, inorganic fiber in rubber or resin.

Inventors: HOSHIKAWA SHINGO, MIYOSHI TAKESHI, TAKAOKA MASAHIKO, UEDA TAKAHISA, HOSHIKAWA, SHINGO, MIYOSHI, TAKESHI, TAKAOKA, MASAHIKO, UEDA, TAKAHISA
Applicants: NIPPON PILLAR PACKING, NIPPON PILLAR PACKING CO., LTD.
Application year: 1994
Main classification: F16J15
IPC codes: F16J15